Frame Relay Networks

1 Abstract Frame relay networks reduce the cost of transmission lines and equipment and improve network performance and response time. Designed for transmission lines with a low error rate, frame relay networks provide minimal internal checking, and consequently, error detection and recovery is implemented in the attached user systems. The Frame Relay Bearer Service was developed specifically as a data service to handle high-volume, bursty traffic by means of high-speed packet transmission, minimal network delay, and efficient use of network bandwidth. The frame protocol supports the data transfer phase of the Service; the frame relay header and the local management interface are sources of congestion avoidance mechanisms. Current implementations include the StrataCom IPX FastPacket digital networking system, which provides the frame relay network, and Digital's DECNIS 500/600 and DEC WANrouter 100/500 software for attaching user equipment. Today's communications networks are built using high-speed digital trunks that inherently provide high throughput, minimal delay, and a very low error rate. Such transmission networks supply highly reliable service without the overhead of error control functions. Frame relay is a packet-mode transmission network service that exploits these network characteristics by minimizing the amount of error detection and recovery performed inside the network. This paper explains the nature of the Frame Relay Bearer Service (FRBS) and provides details of the interface defined for attaching user equipment. The implications for higher-layer protocols in the user equipment are also considered. Following this tutorial, the paper introduces some current implementations. As an example of equipment used to construct a frame relay network, the technology deployed by the StrataCom integrated packet exchange (IPX) FastPacket range of equipment is described. Access to a frame relay network is typically via a router, as is illustrated in the discussion of two Digital products: o The DECNIS V2.1 software, i.e., network integration server, for either the DECNIS 500 or the DECNIS 600 hardware units (abbreviated as DECNIS 500/600) o The DEC WANrouter V1.0 software for either the DEMSB or the DEMSA hardware units (subsequently referred to as the WANrouter 100/500)